Periphery and brain, innate and adaptive immunity in Parkinson's disease

The TLR4/NF-κB/NLRP3 and Nrf2/HO-1 pathways mediate the neuroprotective effects of alkaloids extracted from Uncaria rhynchophylla in Parkinson's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is the second most common neurodegenerative disorder with limited therapeutic options available. Neuroinflammation plays an important role in the occurrence and development of PD. Alkaloids extracted from Uncaria rhynchophylla (URA), have emerged as a potential neuroprotective agent because of its anti-inflammatory and anti-oxidant properties. Nevertheless, the underlying mechanism by which URA exerts neuroprotective effects in PD remains obscure.

AIM OF THE STUDY

The main aim of this study was to investigate the neuroprotective effects and underlying mechanism of URA in the treatment of PD through in vivo and in vitro models, focusing on the neuroinflammation and oxidative stress pathways.

MATERIALS AND METHODS

The protective effects of URA against PD were evaluated by neurobehavioral tests, immunohistochemistry, serum biochemical assays, and real-time quantitative polymerase chain reaction in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice. The role of the TLR4/NF-κB/NLRP3 pathway and the Nrf2/HO-1 pathway in URA-mediated effects was examined in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells and a microglia-neuron coculture system.

RESULTS

URA significantly alleviated motor deficits and dopaminergic neurotoxicity, and reversed the abnormal secretion of inflammatory and oxidative stress factors in the serum of MPTP-induced mice. URA suppressed the gene expression of Toll-like receptor 4 (TLR4), NOD-like receptor protein 3, and cyclooxygenase 2 (COX2) in the striatum of PD mice. Further studies indicated that URA inhibited activation of the TLR4/NF-κB/NLRP3 pathway and enhanced activation of the Nrf2/HO-1 pathway, reduced reactive oxygen species (ROS) production, and reversed the secretion of inflammatory mediators in LPS-stimulated BV-2 microglial cells, thereby alleviating neuroinflammatory damage to SH-SY5Y neuronal cells.

CONCLUSION

URA exerted neuroprotective effects against PD mainly by the inhibition of the TLR4/NF-κB/NLRP3 pathway and activation of the Nrf2/HO-1 antioxidant pathway, highlighting URA as a promising candidate for PD treatment.

The misfolding mystery: α-synuclein and the pathogenesis of Parkinson's disease

Neurodegenerative diseases such as Parkinson's disease (PD) are characterized by the death of neurons in specific areas of the brain. One of the proteins that is involved in the pathogenesis of PD is α-synuclein (α-syn). α-Syn is a normal protein that is found in all neurons, but in PD, it misfolds and aggregates into toxic fibrils. These fibrils can then coalesce into pathological inclusions, such as Lewy bodies and Lewy neurites. The pathogenic pathway of PD is thought to involve a number of steps, including misfolding and aggregation of α-syn, mitochondrial dysfunction, protein clearance impairment, neuroinflammation and oxidative stress. A deeper insight into the structure of α-syn and its fibrils could aid in understanding the disease's etiology. The prion-like nature of α-syn is also an important area of research. Prions are misfolded proteins that can spread from cell to cell, causing other proteins to misfold as well. It is possible that α-syn may behave in a similar way, spreading from cell to cell and causing a cascade of misfolding and aggregation. Various post-translational alterations have also been observed to play a role in the pathogenesis of PD. These alterations can involve a variety of nuclear and extranuclear activities, and they can lead to the misfolding and aggregation of α-syn. A better understanding of the pathogenic pathway of PD could lead to the development of new therapies for the treatment of this disease.

Challenges and Future Perspectives in Modeling Neurodegenerative Diseases Using Organ-on-a-Chip Technology

Neurodegenerative diseases (NDDs) affect more than 50 million people worldwide, posing a significant global health challenge as well as a high socioeconomic burden. With aging constituting one of the main risk factors for some NDDs such as Alzheimer's disease (AD) and Parkinson's disease (PD), this societal toll is expected to rise considering the predicted increase in the aging population as well as the limited progress in the development of effective therapeutics. To address the high failure rates in clinical trials, legislative changes permitting the use of alternatives to traditional pre-clinical in vivo models are implemented. In this regard, microphysiological systems (MPS) such as organ-on-a-chip (OoC) platforms constitute a promising tool, due to their ability to mimic complex and human-specific tissue niches in vitro. This review summarizes the current progress in modeling NDDs using OoC technology and discusses five critical aspects still insufficiently addressed in OoC models to date. Taking these aspects into consideration in the future MPS will advance the modeling of NDDs in vitro and increase their translational value in the clinical setting.

Plasma proteomics identify biomarkers predicting Parkinson's disease up to 7 years before symptom onset

Parkinson's disease is increasingly prevalent. It progresses from the pre-motor stage (characterised by non-motor symptoms like REM sleep behaviour disorder), to the disabling motor stage. We need objective biomarkers for early/pre-motor disease stages to be able to intervene and slow the underlying neurodegenerative process. Here, we validate a targeted multiplexed mass spectrometry assay for blood samples from recently diagnosed motor Parkinson's patients (n = 99), pre-motor individuals with isolated REM sleep behaviour disorder (two cohorts: n = 18 and n = 54 longitudinally), and healthy controls (n = 36). Our machine-learning model accurately identifies all Parkinson patients and classifies 79% of the pre-motor individuals up to 7 years before motor onset by analysing the expression of eight proteins-Granulin precursor, Mannan-binding-lectin-serine-peptidase-2, Endoplasmatic-reticulum-chaperone-BiP, Prostaglaindin-H2-D-isomaerase, Interceullular-adhesion-molecule-1, Complement C3, Dickkopf-WNT-signalling pathway-inhibitor-3, and Plasma-protease-C1-inhibitor. Many of these biomarkers correlate with symptom severity. This specific blood panel indicates molecular events in early stages and could help identify at-risk participants for clinical trials aimed at slowing/preventing motor Parkinson's disease.

TREM-1 mediates interaction between substantia nigra microglia and peripheral neutrophils

JOURNAL/nrgr/04.03/01300535-202406000-00043/inline-graphic1/v/2023-10-30T152229Z/r/image-tiff

Microglia-mediated neuroinflammation is considered a pathological feature of Parkinson’s disease. Triggering receptor expressed on myeloid cell-1 (TREM-1) can amplify the inherent immune response, and crucially, regulate inflammation. In this study, we found marked elevation of serum soluble TREM-1 in patients with Parkinson’s disease that positively correlated with Parkinson’s disease severity and dyskinesia. In a mouse model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson’s disease, we found that microglial TREM-1 expression also increased in the substantia nigra. Further, TREM-1 knockout alleviated dyskinesia in a mouse model of Parkinson’s disease and reduced dopaminergic neuronal injury. Meanwhile, TREM-1 knockout attenuated the neuroinflammatory response, dopaminergic neuronal injury, and neutrophil migration. Next, we established an in vitro 1-methyl-4-phenyl-pyridine-induced BV2 microglia model of Parkinson’s disease and treated the cells with the TREM-1 inhibitory peptide LP17. We found that LP17 treatment reduced apoptosis of dopaminergic neurons and neutrophil migration. Moreover, inhibition of neutrophil TREM-1 activation diminished dopaminergic neuronal apoptosis induced by lipopolysaccharide. TREM-1 can activate the downstream CARD9/NF-κB proinflammatory pathway via interaction with SYK. These findings suggest that TREM-1 may play a key role in mediating the damage to dopaminergic neurons in Parkinson’s disease by regulating the interaction between microglia and peripheral neutrophils.

Systemic immune-inflammation index is associated with cardiac complications following acute ischemic stroke: A retrospective single-center study

BACKGROUND

Stroke-induced heart syndrome is a feared complication of ischemic stroke, that is commonly encountered and has a strong association with unfavorable prognosis. More research is needed to explore underlying mechanisms and inform clinical decision making. This study aims to explore the relationship between the early systemic immune-inflammation (SII) index and the cardiac complications after acute ischemic stroke.

METHODS

Consecutive patients with acute ischemic stroke were prospectively collected from January 2020 to August 2022 and retrospectively analyzed. We included subjects who presented within 24 hours after symptom onset and were free of detectable infections or cancer on admission. SII index [(neutrophils × platelets/ lymphocytes)/1000] was calculated from laboratory data at admission.

RESULTS

A total of 121 patients were included in our study, of which 24 (19.8 %) developed cardiac complications within 14 days following acute ischemic stroke. The SII level was found higher in patients with stroke-heart syndrome (p<.001), which was an independent predictor of stroke-heart syndrome (adjusted odds ratio 5.089, p=.002).

CONCLUSION

New-onset cardiovascular complications diagnosed following a stroke are very common and are associated with early SII index.

Identification of key mitochondria-related genes and their relevance to the immune system linking Parkinson's disease and primary Sjögren's syndrome through integrated bioinformatics analyses

BACKGROUND

Mitochondria are the metabolic hubs of cells, regulating energy production and antigen presentation, which are essential for activation, proliferation, and function of immune cells. Recent evidence indicates that mitochondrial antigen presentation may have an impact on diseases such as Parkinson's disease (PD) and autoimmune diseases. However, there is limited knowledge about the mechanisms that regulate the presentation of mitochondrial antigens in these diseases.

METHODS

In the current study, RNA sequencing was performed on labial minor salivary gland (LSG) from 25 patients with primary Sjögren's syndrome (pSS) and 14 non-pSS aged controls. Additionally, we obtained gene expression omnibus datasets associated with PD patients from NCBI Gene Expression Omnibus (GEO) databases. Single-sample Gene Set Enrichment Analysis (ssGSEA), ESTIMATE and Spearman correlations were conducted to explore the association between mitochondrial related genes and the immune system. Furthermore, we applied weighted Gene Co-expression Network Analysis (WGCNA) to identify hub mitochondria-related genes and investigate the correlated networks in both diseases. Single cell transcriptome analysis, immunohistochemical (IHC) staining and quantitative real-time PCR (qRT-PCR) were used to verify the activation of the hub mitochondria-related pathway. Pearson correlations and the CIBERSORT algorithms were employed to further reveal the correlation between hub mitochondria-related pathways and immune infiltration.

RESULTS

The transcriptome analysis revealed the presence of overlapping mitochondria-related genes and mitochondrial DNA damage in patients with pSS and PD. Reactive oxygen species (ROS), the senescence marker p53, and the inflammatory markers CD45 and Bcl-2 were found to be regionally distributed in LSGs of pSS patients. WGCNA analysis identified the STING pathway as the central mitochondria-related pathway closely associated with the immune system. Single cell analysis, IHC staining, and qRT-PCR confirmed the activation of the STING pathway. Subsequent, bioinformatic analysis revealed the proportion of infiltrating immune cells in the STING-high and STING-low groups of pSS and PD. Furthermore, the study demonstrated the association of the STING pathway with innate and adaptive immune cells, as well as functional cells, in the immune microenvironment of PD and pSS.

CONCLUSION

Our study uncovered a central pathway that connects mitochondrial dysfunction and the immune microenvironment in PD and pSS, potentially offering valuable insights into therapeutic targets for these conditions.

Indoleamine 2,3-dioxygenase (IDO1) - Can dendritic cells and monocytes expressing this moonlight enzyme change the phase of Parkinson's Disease?

Parkinson's Disease (PD) is the second most common neurodegenerative disease where central and peripheral immune dysfunctions have been pointed out as a critical component of susceptibility and progression of this disease. Dendritic cells (DCs) and monocytes are key players in promoting immune response regulation and can induce the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) under pro-inflammatory environments. This enzyme with catalytic and signaling activity supports the axis IDO1-KYN-aryl hydrocarbon receptor (AhR), promoting disease-specific immunomodulatory effects. IDO1 is a rate-limiting enzyme of the kynurenine pathway (KP) that begins tryptophan (Trp) catabolism across this pathway. The immune functions of the pathway, which are extensively described in cancer, have been forgotten so far in neurodegenerative diseases, where a chronic inflammatory environment underlines the progression of the disease. Despite dysfunctions of KP have been described in PD, these are mainly associated with neurotoxic functions. With this review, we aim to focus on the immune properties of IDO1+DCs and IDO1+monocytes as a possible strategy to balance the pro-inflammatory profile described in PD. We also highlight the importance of exploring the role of dopaminergic therapeutics in IDO1 modulation to possibly optimize current PD therapeutic strategies.

The mechanisms of white matter injury and immune system crosstalk in promoting the progression of Parkinson's disease: a narrative review

Parkinson's disease (PD) is neurodegenerative disease in middle-aged and elderly people with some pathological mechanisms including immune disorder, neuroinflammation, white matter injury and abnormal aggregation of alpha-synuclein, etc. New research suggests that white matter injury may be important in the development of PD, but how inflammation, the immune system, and white matter damage interact to harm dopamine neurons is not yet understood. Therefore, it is particularly important to delve into the crosstalk between immune cells in the central and peripheral nervous system based on the study of white matter damage in PD. This crosstalk could not only exacerbate the pathological process of PD but may also reveal new therapeutic targets. By understanding how immune cells penetrate through the blood-brain barrier and activate inflammatory responses within the central nervous system, we can better grasp the impact of structural destruction of white matter in PD and explore how this process can be modulated to mitigate or combat disease progression. Microglia, astrocytes, oligodendrocytes and peripheral immune cells (especially T cells) play a central role in its pathological process where these immune cells produce and respond to pro-inflammatory cytokines such as tumor necrosis factor (TNF-α), interleukin-1β(IL-1β) and interleukin-6(IL-6), and white matter injury causes microglia to become pro-inflammatory and release inflammatory mediators, which attract more immune cells to the damaged area, increasing the inflammatory response. Moreover, white matter damage also causes dysfunction of blood-brain barrier, allows peripheral immune cells and inflammatory factors to invade the brain further, and enhances microglia activation forming a vicious circle that intensifies neuroinflammation. And these factors collectively promote the neuroinflammatory environment and neurodegeneration changes of PD. Overall, these findings not only deepen our understanding of the complexity of PD, but also provide new targets for the development of therapeutic strategies focused on inflammation and immune regulation mechanisms. In summary, this review provided the theoretical basis for clarifying the pathogenesis of PD, summarized the association between white matter damage and the immune cells in the central and peripheral nervous systems, and then emphasized their potential specific mechanisms of achieving crosstalk with further aggravating the pathological process of PD.

CAP2 contributes to Parkinson's disease diagnosed by neutrophil extracellular trap-related immune activity

Introduction

Neutrophil extracellular traps (NETs) constitute a crucial element of the immune system, and dysfunction in immune responses is implicated in the susceptibility and progression of Parkinson's disease (PD). Nevertheless, the mechanism connecting PD and NETs remains unclear. This study aims to uncover potential NETs-related immune biomarkers and elucidate their role in PD pathogenesis.

Methods

Through differential gene analysis of PD and NETs in GSE7621 datasets, we identified two PD subtypes and explored potential biological pathways. Subsequently, using ClusterWGCNA, we pinpointed pertinent genes and developed clinical diagnostic models. We then optimized the chosen model and evaluated its association with immune infiltration. Validation was conducted using the GSE20163 dataset. Screening the single-cell dataset GSE132758 revealed cell populations associated with the identified gene.

Results

Our findings identified XGB as the optimal diagnostic model, with CAP2 identified as a pivotal gene. The risk model effectively predicted overall diagnosis rates, demonstrating a robust correlation between infiltrating immune cells and genes related to the XGB model.

Discussion

In conclusions, we identified PD subtypes and diagnostic genes associated with NETs, highlighting CAP2 as a pivotal gene. These findings have significant implications for understanding potential molecular mechanisms and treatments for PD.

Integrated Bioinformatics Analysis for Revealing CBL is a Potential Diagnosing Biomarker and Related Immune Infiltration in Parkinson's Disease

Purpose

There is growing evidence that the immune system plays an important role in the progression of Parkinson's disease, the second most common neurodegenerative disorder. This study aims to address the comprehensive understanding of the immunopathogenesis of Parkinson's disease and explore new inflammatory biomarkers.

Patients and Methods

In this study, Immune-related differential expressed genes (DEIRGs) were obtained from GEO database and Immport database. The hub gene was screened in DEIRGs using LASSO regression and random forest algorithm, and the mRNA expression of the identified hub gene was validated using clinical blood samples.

Results

We obtained a total of 157 DEIRGs that played an important role in the immune response. The results of immune cell infiltration analysis showed that the degree of memory B cells infiltration was higher in PD patients, while the degree of Monocytes, resting mast cells and M0 macrophages infiltration was lower (p<0.05). A total of 8 hub genes were screened by machine learning methods, and RT-PCR results showed that the expression level of CBL gene in PD was significantly increased (p<0.05).

Conclusion

Our findings suggest that CBL is a new potential diagnostic biomarker for PD and that abnormal immune cell infiltration may influence PD development.

Hiding in plain sight: Do recruited dendritic cells surround amyloid plaques in Alzheimer's disease?

Over the past decade, human genome-wide association and expression studies have strongly implicated dysregulation of the innate immune system in the pathogenesis of Alzheimer's disease (AD). Single cell mRNA sequencing studies have identified innate immune cell subtypes that are minimally present in normal healthy brain, but whose numbers greatly increase in association with AD pathology. These AD pathology-associated immune cells are putatively the locus for the immune-related AD risk. While the prevailing view is that these immune cells arise from transformation of resident brain microglia, studies across several decades and using multiple techniques and strategies suggest instead that the pathology-associated immune cells are bone-marrow derived hematopoietic cells that are recruited into brain. We critically review this translational literature, emphasizing the strengths and limitations of techniques used to address recruitment and the experimental designs employed. We conclude that the aggregate evidence points toward recruitment into brain of innate immune cells of the myeloid dendritic cell lineage. Recruitment of dendritic cells and their role in AD pathogenesis has broad implications for our understanding of the etiology and pathobiology of AD that impact the strategies to develop new, immune system-targeted therapeutics for this devastating disease.

The major histocompatibility complex participates in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by progressive loss of dopaminergic neurons in the substantia nigra and the aggregation of alpha-synuclein (α-syn). The central nervous system (CNS) has previously been considered as an immune-privileged area. However, studies have shown that the immune responses are involved in PD. The major histocompatibility complex (MHC) presents antigens from antigen-presenting cells (APCs) to T lymphocytes, immune responses will be induced. MHCs are expressed in microglia, astrocytes, and dopaminergic neurons. Single nucleotide polymorphisms in MHC are related to the risk of PD. The aggregated α-syn triggers the expression of MHCs by activating glia cells. CD4+ and CD8+ T lymphocytes responses and microglia activation are detected in brains of PD patients. In addiction immune responses further increase blood-brain barrier (BBB) permeability and T cell infiltration in PD. Thus, MHCs are involved in PD through participating in immune and inflammatory responses.

Mood disturbances in newly diagnosed Parkinson's Disease patients reflect intrathecal inflammation

In Parkinson's disease (PD), neuroinflammation may be involved in the pathogenesis of mood disorders, contributing to the clinical heterogeneity of the disease. The cerebrospinal fluid (CSF) levels of interleukin (IL)-1β, IL-2, IL-6, IL-7, IL-8, IL-9, IL-12, IL-17, interferon (IFN)γ, macrophage inflammatory protein 1-alpha (MIP-1a), MIP-1b, granulocyte colony stimulating factor (GCSF), eotaxin, tumor necrosis factor (TNF), and monocyte chemoattractant protein 1 (MCP-1), were assessed in 45 newly diagnosed and untreated PD patients and in 44 control patients. Spearman's correlations were used to explore possible associations between CSF cytokines and clinical variables including mood. Benjamini-Hochberg (B-H) correction for multiple comparisons was applied. Linear regression was used to test significant associations correcting for other clinical variables. In PD patients, higher CSF concentrations of the inflammatory molecules IL-6, IL-9, IFNγ, and GCSF were found (all B-H corrected p < 0.02). Significant associations were found between BDI-II and the levels of IL-6 (Beta = 0.438; 95%CI 1.313-5.889; p = 0.003) and IL-8 (Beta = 0.471; 95%CI 0.185-0.743; p = 0.002). Positive associations were also observed between STAI-Y state and both IL-6 (Beta = 0.452; 95%CI 1.649-7.366; p = 0.003), and IL-12 (Beta = 0.417; 95%CI 2.238-13.379; p = 0.007), and between STAI-Y trait and IL-2 (Beta = 0.354; 95%CI 1.923-14.796; p = 0.012), IL-6 (Beta = 0.362; 95%CI 0.990-6.734; p = 0.01), IL-8 (Beta = 0.341; 95%CI 0.076-0.796; p = 0.019), IL-12 (Beta = 0.328; 95%CI 0.975-12.135; p = 0.023), and IL-17 (Beta = 0.334; 95CI 0.315-4.455; p = 0.025). An inflammatory CSF milieu may be associated with depression and anxiety in the early phases of PD, supporting a role of neuroinflammation in the pathogenesis of mood disturbances.

The role of the brain renin-angiotensin system in Parkinson´s disease

The renin-angiotensin system (RAS) was classically considered a circulating hormonal system that regulates blood pressure. However, different tissues and organs, including the brain, have a local paracrine RAS. Mutual regulation between the dopaminergic system and RAS has been observed in several tissues. Dysregulation of these interactions leads to renal and cardiovascular diseases, as well as progression of dopaminergic neuron degeneration in a major brain center of dopamine/angiotensin interaction such as the nigrostriatal system. A decrease in the dopaminergic function induces upregulation of the angiotensin type-1 (AT1) receptor activity, leading to recovery of dopamine levels. However, AT1 receptor overactivity in dopaminergic neurons and microglial cells upregulates the cellular NADPH-oxidase-superoxide axis and Ca2+ release, which mediate several key events in oxidative stress, neuroinflammation, and α-synuclein aggregation, involved in Parkinson's disease (PD) pathogenesis. An intraneuronal antioxidative/anti-inflammatory RAS counteracts the effects of the pro-oxidative AT1 receptor overactivity. Consistent with this, an imbalance in RAS activity towards the pro-oxidative/pro-inflammatory AT1 receptor axis has been observed in the substantia nigra and striatum of several animal models of high vulnerability to dopaminergic degeneration. Interestingly, autoantibodies against angiotensin-converting enzyme 2 and AT1 receptors are increased in PD models and PD patients and contribute to blood-brain barrier (BBB) dysregulation and nigrostriatal pro-inflammatory RAS upregulation. Therapeutic strategies addressed to the modulation of brain RAS, by AT1 receptor blockers (ARBs) and/or activation of the antioxidative axis (AT2, Mas receptors), may be neuroprotective for individuals with a high risk of developing PD or in prodromal stages of PD to reduce progression of the disease.

Nigrostriatal degeneration determines dynamics of glial inflammatory and phagocytic activity

Glial cells are key players in the initiation of innate immunity in neurodegeneration. Upon damage, they switch their basal activation state and acquire new functions in a context and time-dependent manner. Since modulation of neuroinflammation is becoming an interesting approach for the treatment of neurodegenerative diseases, it is crucial to understand the specific contribution of these cells to the inflammatory reaction and to select experimental models that recapitulate what occurs in the human disease. Previously, we have characterized a region-specific activation pattern of CD11b+ cells and astrocytes in the α-synuclein overexpression mouse model of Parkinson´s disease (PD). In this study we hypothesized that the time and the intensity of dopaminergic neuronal death would promote different glial activation states. Dopaminergic degeneration was induced with two administration regimens of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), subacute (sMPTP) and chronic (cMPTP). Our results show that in the sMPTP mouse model, the pro-inflammatory phenotype of striatal CD11b+ cells was counteracted by an anti-inflammatory astrocytic profile. In the midbrain the roles were inverted, CD11b+ cells exhibited an anti-inflammatory profile and astrocytes were pro-inflammatory. The overall response generated resulted in decreased CD4 T cell infiltration in both regions. Chronic MPTP exposure resulted in a mild and prolonged neuronal degeneration that generated a pro-inflammatory response and increased CD4 T cell infiltration in both regions. At the onset of the neurodegenerative process, microglia and astrocytes cooperated in the removal of dopaminergic terminals. With time, only microglia maintained the phagocytic activity. In the ventral midbrain, astrocytes were the main phagocytic mediators at early stages of degeneration while microglia were the major phagocytic cells in the chronic state. In this scenario, we questioned which activation pattern recapitulates better the features of glial activation in PD. Glial activation in the cMPTP mouse model reflects many pathways of their corresponding counterparts in the human brain with advanced PD. Altogether, our results point toward a context-dependent cooperativity of microglia/myeloid cells and astrocytes in response to neuronal damage and the relevance of selecting the right experimental models for the study of neuroinflammation.

The role of T-lymphocytes in central nervous system diseases

The central nervous system (CNS) has been considered an immunologically privileged site. In the past few decades, research on inflammation in CNS diseases has mostly focused on microglia, innate immune cells that respond rapidly to injury and infection to maintain CNS homeostasis. Discoveries of lymphatic vessels within the dura mater and peripheral immune cells in the meningeal layer indicate that the peripheral immune system can monitor and intervene in the CNS. This review summarizes recent advances in the involvement of T lymphocytes in multiple CNS diseases, including brain injury, neurodegenerative diseases, and psychiatric disorders. It emphasizes that a deep understanding of the pathogenesis of CNS diseases requires intimate knowledge of T lymphocytes. Aiming to promote a better understanding of the relationship between the immune system and CNS and facilitate the development of therapeutic strategies targeting T lymphocytes in neurological diseases.

Immune cells: potential carriers or agents for drug delivery to the central nervous system

Drug delivery systems (DDS) have recently emerged as a promising approach for the unique advantages of drug protection and targeted delivery. However, the access of nanoparticles/drugs to the central nervous system (CNS) remains a challenge mainly due to the obstruction from brain barriers. Immune cells infiltrating the CNS in the pathological state have inspired the development of strategies for CNS foundation drug delivery. Herein, we outline the three major brain barriers in the CNS and the mechanisms by which immune cells migrate across the blood-brain barrier. We subsequently review biomimetic strategies utilizing immune cell-based nanoparticles for the delivery of nanoparticles/drugs to the CNS, as well as recent progress in rationally engineering immune cell-based DDS for CNS diseases. Finally, we discuss the challenges and opportunities of immune cell-based DDS in CNS diseases to promote their clinical development.

Ultrasound-Assisted CRISPRi-Exosome for Epigenetic Modification of α-Synuclein Gene in a Mouse Model of Parkinson's Disease

Currently, there is a lack of effective treatment for Parkinson's disease (PD). In PD patients, aberrant methylation of SNCA (α-synuclein gene) has been reported and may be a potential therapeutic target. In this study, we established an epigenetic regulation platform based on an exosomal CRISPR intervention system. With the assist of focused ultrasound (FUS) opening the blood-brain barrier, engineered exosomes carrying RVG (rabies viral glycoprotein) targeting peptide, sgRNA (single guide RNA), and dCas9-DNMT3A (named RVG-CRISPRi-Exo) were efficiently delivered into the brain lesions and induced specific methylation of SNCA. In vivo, FUS combined with RVG-CRISPRi-Exo significantly improved motor performance, balance coordination, and neurosensitivity in PD mice, greatly down-regulated the elevation of α-synuclein (α-syn) caused by modeling, rescued cell apoptosis, and alleviated the progression of PD in mice. [18F]-FP-DTBZ imaging suggested that the synaptic function of the nigrostriatal pathway could be restored, which was conducive to the control of motor behavior in PD mice. Pyrosequencing results showed that RVG-CRISPRi-Exo could methylate CpG at specific sites of SNCA, and this fine-tuned editing achieved good therapeutic effects in PD model mice. In vitro, RVG-CRISPRi-Exo down-regulated SNCA transcripts and α-syn expression and relieved neuronal cell damage. Collectively, our findings provide a proof-of-principle for the development of targeted brain nanodelivery based on engineered exosomes and provide insights into epigenetic regulation of brain diseases.

A potential mechanism clue to the periodic storm from microglia activation and progressive neuron damage induced by paraquat exposure

Paraquat (PQ), is characterized by neurotoxicity, which increases the potential risk of Parkinson's disease (PD) exposure in the long-term and low doses. Triggering microglia activation and neuroinflammation is deemed an early event resulting in PD. However, the underlying pathogenesis of PD by PQ is not clear yet. In this article, C57BL/6J mice treated with PQ could successfully act out Parkinson-like. In addition, we observed the fluorescence intensity enhancement of Iba-1 activated microglia with released pro-inflammatory, all ahead of both the damage of dopaminergic neurons in the substantia nigra and corpus striatum of the brain. Surprisingly, the injection of minocycline before PQ for many hours not only can effectively improve the neurobehavioral symptoms of mice but inhibit the activation of microglia and the release of pro-inflammatory substances, even controlling the gradual damage and loss of neurons. A further mechanism of minocycline hampered the expression levels of key signaling proteins PI3K, PDK1, p-AKT, and CD11b (the receptor of microglia membrane recognition), while a large number of inflammatory factors. Our results suggested that the CD11b/PI3K/NOX2 pathway may be a clue that microglia-mediated inflammatory responses and neuronal damage in a PQ-induced abnormal behavior Parkinson-like mouse.

Neuroimmune interactions and their roles in neurodegenerative diseases

The nervous system possesses bidirectional, sophisticated and delicate communications with the immune system. These neuroimmune interactions play a vitally important role in the initiation and development of many disorders, especially neurodegenerative diseases. Although scientific advancements have made tremendous progress in this field during the last few years, neuroimmune communications are still far from being elucidated. By organizing recent research, in this review, we discuss the local and intersystem neuroimmune interactions and their roles in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Unveiling these will help us gain a better understanding of the process of interplay inside the body and how the organism maintains homeostasis. It will also facilitate a view of the diseases from a holistic, pluralistic and interconnected perspective, thus providing a basis of developing novel and effective methods to diagnose, intervene and treat diseases.

Screening of key immunerelated gene in Parkinsons disease based on WGCNA and machine learning

OBJECTIVES

Abnormal immune system activation and inflammation are crucial in causing Parkinson's disease. However, we still don't fully understand how certain immune-related genes contribute to the disease's development and progression. This study aims to screen key immune-related gene in Parkinson's disease based on weighted gene co-expression network analysis (WGCNA) and machine learning.

METHODS

This study downloaded the gene chip data from the Gene Expression Omnibus (GEO) database, and used WGCNA to screen out important gene modules related to Parkinson's disease. Genes from important modules were exported and a Venn diagram of important Parkinson's disease-related genes and immune-related genes was drawn to screen out immune related genes of Parkinson's disease. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the the functions of immune-related genes and signaling pathways involved. Immune cell infiltration analysis was performed using the CIBERSORT package of R language. Using bioinformatics method and 3 machine learning methods [least absolute shrinkage and selection operator (LASSO) regression, random forest (RF), and support vector machine (SVM)], the immune-related genes of Parkinson's disease were further screened. A Venn diagram of differentially expressed genes screened using the 4 methods was drawn with the intersection gene being hub nodes (hub) gene. The downstream proteins of the Parkinson's disease hub gene was identified through the STRING database and a protein-protein interaction network diagram was drawn.

RESULTS

A total of 218 immune genes related to Parkinson's disease were identified, including 45 upregulated genes and 50 downregulated genes. Enrichment analysis showed that the 218 genes were mainly enriched in immune system response to foreign substances and viral infection pathways. The results of immune infiltration analysis showed that the infiltration percentages of CD4+ T cells, NK cells, CD8+ T cells, and B cells were higher in the samples of Parkinson's disease patients, while resting NK cells and resting CD4+ T cells were significantly infiltrated in the samples of Parkinson's disease patients. ANK1 was screened out as the hub gene. The analysis of the protein-protein interaction network showed that the ANK1 translated and expressed 11 proteins which mainly participated in functions such as signal transduction, iron homeostasis regulation, and immune system activation.

CONCLUSIONS

This study identifies the Parkinson's disease immune-related key gene ANK1 via WGCNA and machine learning methods, suggesting its potential as a candidate therapeutic target for Parkinson's disease.

Therapeutics for neurodegenerative diseases by targeting the gut microbiome: from bench to bedside

The aetiologies and origins of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD), are complex and multifaceted. A growing body of evidence suggests that the gut microbiome plays crucial roles in the development and progression of neurodegenerative diseases. Clinicians have come to realize that therapeutics targeting the gut microbiome have the potential to halt the progression of neurodegenerative diseases. This narrative review examines the alterations in the gut microbiome in AD, PD, ALS and HD, highlighting the close relationship between the gut microbiome and the brain in neurodegenerative diseases. Processes that mediate the gut microbiome-brain communication in neurodegenerative diseases, including the immunological, vagus nerve and circulatory pathways, are evaluated. Furthermore, we summarize potential therapeutics for neurodegenerative diseases that modify the gut microbiome and its metabolites, including diets, probiotics and prebiotics, microbial metabolites, antibacterials and faecal microbiome transplantation. Finally, current challenges and future directions are discussed.

The insular cortex is not insular in thyroid eye disease: neuroimaging revelations of central-peripheral system interaction

BACKGROUND

Thyroid eye disease (TED) is highly correlated with dysregulated immunoendocrine status. The insular cortex was found to regulate peripheral inflammation and immunomodulation in mice. This study aimed to explore whether the insular cortex in patients with TED played a modulatory role including the aberrant brain functional alteration and its association with immunoendocrine status.

METHODS

This study included 34 active patients (AP), 30 inactive patients (IP) with TED, and 45 healthy controls (HC) matched for age, sex, and educational level. Comprehensive clinical details (especially immunoendocrine markers) and resting-state functional magnetic resonance imaging data were collected from each participant. The amplitude of low-frequency fluctuation (ALFF) was used to probe the aberrant alterations of local neural activity. The seed-based functional connectivity (FC) analysis was used to explore the relationship between the insular cortex and each voxel throughout the whole brain. The correlation analysis was conducted to assess the association between insular neurobiomarkers and immunoendocrine parameters.

RESULTS

When compared with the IP and HC groups, the AP group displayed significantly higher ALFF values in the right insular cortex (INS.R) and lower FC values between the INS.R and the bilateral cerebellum. None of the neurobiomarkers differed between the IP and HC groups. Besides, correlations between insular neurobiomarkers and immunoendocrine markers (free thyroxine, the proportion of T cells, and natural killer cells) were identified in both AP and IP groups.

CONCLUSIONS

This study was novel in reporting that the dysregulation of the insular cortex activity in TED was associated with abnormal peripheral immunoendocrine status. The insular cortex might play a key role in central-peripheral system interaction in TED. Further research is crucial to enhance our understanding of the central-peripheral system interaction mechanisms involved in autoimmune diseases.

The contribution of β-amyloid, Tau and α-synuclein to blood-brain barrier damage in neurodegenerative disorders

Central nervous system (CNS) accumulation of fibrillary deposits made of Amyloid β (Aβ), hyperphosphorylated Tau or α-synuclein (α-syn), present either alone or in the form of mixed pathology, characterizes the most common neurodegenerative diseases (NDDs) as well as the aging brain. Compelling evidence supports that acute neurological disorders, such as traumatic brain injury (TBI) and stroke, are also accompanied by increased deposition of toxic Aβ, Tau and α-syn species. While the contribution of these pathological proteins to neurodegeneration has been experimentally ascertained, the cellular and molecular mechanisms driving Aβ, Tau and α-syn-related brain damage remain to be fully clarified. In the last few years, studies have shown that Aβ, Tau and α-syn may contribute to neurodegeneration also by inducing and/or promoting blood-brain barrier (BBB) disruption. These pathological proteins can affect BBB integrity either directly by affecting key BBB components such as pericytes and endothelial cells (ECs) or indirectly, by promoting brain macrophages activation and dysfunction. Here, we summarize and critically discuss key findings showing how Aβ, Tau and α-syn can contribute to BBB damage in most common NDDs, TBI and stroke. We also highlight the need for a deeper characterization of the role of these pathological proteins in the activation and dysfunction of brain macrophages, pericytes and ECs to improve diagnosis and treatment of acute and chronic neurological disorders.

Neuroinflammatory disease signatures in SPG11-related hereditary spastic paraplegia patients

Biallelic loss of SPG11 function constitutes the most frequent cause of complicated autosomal recessive hereditary spastic paraplegia (HSP) with thin corpus callosum, resulting in progressive multisystem neurodegeneration. While the impact of neuroinflammation is an emerging and potentially treatable aspect in neurodegenerative diseases and leukodystrophies, the role of immune cells in SPG11-HSP patients is unknown. Here, we performed a comprehensive immunological characterization of SPG11-HSP, including examination of three human postmortem brain donations, immunophenotyping of patients' peripheral blood cells and patient-specific induced pluripotent stem cell-derived microglia-like cells (iMGL). We delineate a previously unknown role of innate immunity in SPG11-HSP. Neuropathological analysis of SPG11-HSP patient brain tissue revealed profound microgliosis in areas of neurodegeneration, downregulation of homeostatic microglial markers and cell-intrinsic accumulation of lipids and lipofuscin in IBA1+ cells. In a larger cohort of SPG11-HSP patients, the ratio of peripheral classical and intermediate monocytes was increased, along with increased serum levels of IL-6 that correlated with disease severity. Stimulation of patient-specific iMGLs with IFNγ led to increased phagocytic activity compared to control iMGL as well as increased upregulation and release of proinflammatory cytokines and chemokines, such as CXCL10. On a molecular basis, we identified increased STAT1 phosphorylation as mechanism connecting IFNγ-mediated immune hyperactivation and SPG11 loss of function. STAT1 expression was increased both in human postmortem brain tissue and in an Spg11-/- mouse model. Application of an STAT1 inhibitor decreased CXCL10 production in SPG11 iMGL and rescued their toxic effect on SPG11 neurons. Our data establish neuroinflammation as a novel disease mechanism in SPG11-HSP patients and constitute the first description of myeloid cell/ microglia activation in human SPG11-HSP. IFNγ/ STAT1-mediated neurotoxic effects of hyperreactive microglia upon SPG11 loss of function indicate that immunomodulation strategies may slow down disease progression.

Investigating the TLR4/TAK1/IRF7 axis in NLRP3-Mediated Pyroptosis in Parkinson's Disease

In the realm of Parkinson's disease (PD) research, NLRP3 inflammasome-mediated pyroptosis has recently garnered significant attention as a potential novel form of dopaminergic neuronal death. Our previous research revealed the activation of innate immune-related genes, such as the TLR4 signaling pathway and interferon regulatory factor 7 (IRF7), although the specific mechanism remains unclear. Our current study shed light on whether the TLR4 signaling pathway and IRF7 can affect the pyroptosis of dopaminergic nerve cells and thus participate in the pathogenesis of PD. The PD model was constructed by MPP+ treatment of PC12 cells or stereotactic injection of the striatum of SD rats, and the expression of genes were detected by RT-qPCR and Western Blotting. Lentivirus, siRNA and (5Z)-7-Oxozeaenol were used to validate the regulation of this pathway on pyroptosis. The expression of TLR4, TAK1, IRF7 and pyroptosis molecular markers was upregulated after MPP+ treatment. IRF7 could affect dopaminergic neural cells pyroptosis by targeted regulation of NLRP3. Furthermore, inhibition of the TLR4/TAK1 signaling pathway led to a decrease in the expression of both IRF7 and NLRP3, while overexpression of IRF7 reversed the reduction in pyroptosis and increase in TH expression. TLR4/TAK1/IRF7 axis can promote PD by influencing pyroptosis through NLRP3.

The interplay between neuroinflammatory pathways and Parkinson's disease

Parkinson's disease, a progressive neurodegenerative disorder predominantly affecting elderly, is marked by the gradual degeneration of the nigrostriatal dopaminergic pathway, culminating in neuronal loss within the substantia nigra pars compacta (SNpc) and dopamine depletion. At the molecular level, neuronal loss in the SNpc has been attributed to factors including neuroinflammation, impaired protein homeostasis, as well as mitochondrial dysfunction and the resulting oxidative stress. This review focuses on the interplay between neuroinflammatory pathways and Parkinson's disease, drawing insights from current literature.

Causal relationship between immune cells and neurodegenerative diseases: a two-sample Mendelian randomisation study

Background

There is increasing evidence that the types of immune cells are associated with various neurodegenerative diseases. However, it is currently unclear whether these associations reflect causal relationships.

Objective

To elucidate the causal relationship between immune cells and neurodegenerative diseases, we conducted a two-sample Mendelian randomization (MR) analysis.

Materials and methods

The exposure and outcome GWAS data used in this study were obtained from an open-access database (https://gwas.mrcieu.ac.uk/), the study employed two-sample MR analysis to assess the causal relationship between 731 immune cell features and four neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). All immune cell data was obtained from Multiple MR methods were used to minimize bias and obtain reliable estimates of the causal relationship between the variables of interest and the outcomes. Instrumental variable selection criteria were restricted to ensure the accuracy and effectiveness of the causal relationship between species of immune cells and the risk of these neurodegenerative diseases.

Results

The study identified potential causal relationships between various immune cells and different neurodegenerative diseases. Specifically, we found that 8 different types of immune cells have potential causal relationships with AD, 1 type of immune cells has potential causal relationships with PD, 6 different types of immune cells have potential causal relationships with ALS, and 6 different types of immune cells have potential causal relationships with MS.

Conclusion

Our study, through genetic means, demonstrates close causal associations between the specific types of immune cells and AD, PD, ALS and MS, providing useful guidance for future clinical researches.

MicroRNA-218-5p-Ddx41 axis restrains microglia-mediated neuroinflammation through downregulating type I interferon response in a mouse model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN). Microglia-mediated neuroinflammation has been largely considered one of main factors to the PD pathology. MicroRNA-218-5p (miR-218-5p) is a microRNA that plays a role in neurodevelopment and function, while its potential function in PD and neuroinflammation remains unclear.

METHODS

We explore the involvement of miR-218-5p in the PD in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model. The miR-218-5p agomir used for overexpression was delivered into the substantia nigra (SN) by bilateral stereotaxic infusions. The loss of dopaminergic (DA) neurons and microglial inflammation in the SN was determined using Western blotting and immunofluorescence. Motor function was assessed using the rotarod test. RNA sequencing (RNA-seq) was performed to explore the pathways regulated by miR-218-5p. The target genes of miR-218-5p were predicted using TargetScan and confirmed using dual luciferase reporter assays. The effects of miR-218-5p on microglial inflammation and related pathways were verified in murine microglia-like BV2 cells. To stimulate BV2 cells, SH-SY5Y cells were treated with 1-methyl-4-phenylpyridinium (MPP+) and the conditioned media (CM) were collected.

RESULTS

MiR-218-5p expression was reduced in both the SN of MPTP-induced mice and MPP+-treated BV2 cells. MiR-218-5p overexpression significantly alleviated MPTP-induced microglial inflammation, loss of DA neurons, and motor dysfunction. RNA sequence and gene set enrichment analysis showed that type I interferon (IFN-I) pathways were upregulated in MPTP-induced mice, while this upregulation was reversed by miR-218-5p overexpression. A luciferase reporter assay verified that Ddx41 was a target gene of miR-218-5p. In vitro, miR-218-5p overexpression or Ddx41 knockdown inhibited the IFN-I response and expression of inflammatory cytokines in BV2 cells stimulated with MPP+-CM.

CONCLUSIONS

MiR-218-5p suppresses microglia-mediated neuroinflammation and preserves DA neurons via Ddx41/IFN-I. Hence, miR-218-5p-Ddx41 is a promising therapeutic target for PD.

Differential profiles of serum cytokines in Parkinson's disease according to disease duration

OBJECTIVE

Neurodegeneration and neuroinflammation are two intertwined mechanisms contributing to the pathophysiology of Parkinson's disease. Whether circulating biomarkers reflecting those two processes differ according to disease duration remains to be established. The present study was conducted to characterize the biomarkers individuals with PD with short (≤5 years) or long disease duration (>5 years).

METHODS

We consecutively enrolled 104 patients with Parkinson's disease and evaluated them using validated clinical scales (MDS-UPDRS, Hoehn and Yahr staging, MMSE). Serum samples were assayed for the following biomarkers: neurofilament light chain (NfL), brain-derived neurotrophic factor (BDNF), interleukin (IL-) 1β, 4, 5, 6, 10, 17, interferon-γ, and tumor necrosis factor α.

RESULTS

Mean age of participants was 66.0 ± 9.6 years and 45 (34%) were women. The average disease duration was 8 ± 5 years (range 1 to 19 years). Patients with short disease duration (≤ 5 years) showed a pro-inflammatory profile, with significantly higher levels of pro-inflammatory IL-1β and lower concentrations of IL-5, IL-10 and IL-17 (p < 0.05). NfL serum levels showed a positive correlation with disease duration and age (respectively rho = 0.248, p = 0.014 and rho = 0.559, p < 0.001) while an opposite pattern was detected for BDNF (respectively rho -0,187, p = 0.034 and rho = -0.245, p = 0.014).

CONCLUSIONS

Our findings suggest that a pro-inflammatory status may be observed in PD patients in the early phases of the disease, independently from age.

Inflammation, Autoimmunity and Neurodegenerative Diseases, Therapeutics and Beyond

Neurodegenerative disease (ND) incidence has recently increased due to improved life expectancy. Alzheimer's (AD) or Parkinson's disease (PD) are the most prevalent NDs. Both diseases are poly genetic, multifactorial and heterogenous. Preventive medicine, a healthy diet, exercise, and controlling comorbidities may delay the onset. After the diseases are diagnosed, therapy is needed to slow progression. Recent studies show that local, peripheral and age-related inflammation accelerates NDs' onset and progression. Patients with autoimmune disorders like inflammatory bowel disease (IBD) could be at higher risk of developing AD or PD. However, no increase in ND incidence has been reported if the patients are adequately diagnosed and treated. Autoantibodies against abnormal tau, β amyloid and α- synuclein have been encountered in AD and PD and may be protective. This discovery led to the proposal of immune-based therapies for AD and PD involving monoclonal antibodies, immunization/ vaccines, pro-inflammatory cytokine inhibition and anti-inflammatory cytokine addition. All the different approaches have been analysed here. Future perspectives on new therapeutic strategies for both disorders are concisely examined.

Association of allergic disease with Parkinson's disease: A nationally representative retrospective cohort study

BACKGROUND

The association of allergic diseases such as allergic rhinitis, asthma, and atopic dermatitis with Parkinson's disease (PD) risk is yet unclear. In the few preceding studies, a short follow-up duration was followed for a relatively small study population, and lifestyle behaviors were not adjusted for. Therefore, there is a need for large-scale observation studies on the association of allergic disease with PD risk after considering lifestyle behaviors.

METHODS

The study population consisted of 398,936 participants aged 40 years or older who underwent health screening before 1 January 2005 from the Korean National Health Insurance Service database. Starting from 1 January 2005, all participants were followed up until the date of PD event, death, or 31 December 2019. The adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for the risk of PD were calculated using multivariable Cox proportional hazards regression.

RESULTS

Compared to non-allergic disease participants, allergic disease patients had a higher risk for PD (aHR 1.18, 95% CI 1.07-1.30) and especially, allergic rhinitis patients had a higher risk for PD (aHR 1.14, 95% CI 1.00-1.29). Allergic disease was associated with a higher risk for PD (aHR 1.24, 95% CI 1.01-1.52) among participants who were never smokers, did not consume alcohol, and exercised regularly.

CONCLUSIONS

Allergic rhinitis was associated with a higher risk for PD compared to participants without allergic rhinitis. This risk-increasing association of allergic rhinitis with PD was preserved even among people with healthy lifestyle behaviors.

The role of sphingosine-1-phosphate in the development and progression of Parkinson's disease

Parkinson's disease (PD) could be viewed as a proteinopathy caused by changes in lipids, whereby modifications in lipid metabolism may lead to protein alterations, such as the accumulation of alpha-synuclein (α-syn), ultimately resulting in neurodegeneration. Although the loss of dopaminergic neurons in the substantia nigra is the major clinical manifestation of PD, the etiology of it is largely unknown. Increasing evidence has highlighted the important role of lipids in the pathophysiology of PD. Sphingosine-1-phosphate (S1P), a signaling lipid, has been suggested to have a potential association with the advancement and worsening of PD. Therefore, better understanding the mechanisms and regulatory proteins is of high interest. Most interestingly, S1P appears to be an important target to offers a new strategy for the diagnosis and treatment of PD. In this review, we first introduce the basic situation of S1P structure, function and regulation, with a special focus on the several pathways. We then briefly describe the regulation of S1P signaling pathway on cells and make a special focused on the cell growth, proliferation and apoptosis, etc. Finally, we discuss the function of S1P as potential therapeutic target to improve the clinical symptoms of PD, and even prevent the progression of the PD. In the context of PD, the functions of S1P modulators have been extensively elucidated. In conclusion, S1P modulators represent a novel and promising therapeutic principle and therapeutic method for PD. However, more research is required before these drugs can be considered as a standard treatment option for PD.

Regulation of Pain Perception by Microbiota in Parkinson Disease

Pain perception involves current stimulation in peripheral nociceptive nerves and the subsequent stimulation of postsynaptic excitatory neurons in the spinal cord. Importantly, in chronic pain, the neural activity of both peripheral nociceptors and postsynaptic neurons in the central nervous system is influenced by several inflammatory mediators produced by the immune system. Growing evidence has indicated that the commensal microbiota plays an active role in regulating pain perception by either acting directly on nociceptors or indirectly through the modulation of the inflammatory activity on immune cells. This symbiotic relationship is mediated by soluble bacterial mediators or intrinsic structural components of bacteria that act on eukaryotic cells, including neurons, microglia, astrocytes, macrophages, T cells, enterochromaffin cells, and enteric glial cells. The molecular mechanisms involve bacterial molecules that act directly on neurons, affecting their excitability, or indirectly on non-neuronal cells, inducing changes in the production of proinflammatory or anti-inflammatory mediators. Importantly, Parkinson disease, a neurodegenerative and inflammatory disorder that affects mainly the dopaminergic neurons implicated in the control of voluntary movements, involves not only a motor decline but also nonmotor symptomatology, including chronic pain. Of note, several recent studies have shown that Parkinson disease involves a dysbiosis in the composition of the gut microbiota. In this review, we first summarize, integrate, and classify the molecular mechanisms implicated in the microbiota-mediated regulation of chronic pain. Second, we analyze the changes on the commensal microbiota associated to Parkinson disease and propose how these changes affect the development of chronic pain in this pathology. SIGNIFICANCE STATEMENT: The microbiota regulates chronic pain through the action of bacterial signals into two main locations: the peripheral nociceptors and the postsynaptic excitatory neurons in the spinal cord. The dysbiosis associated to Parkinson disease reveals increased representation of commensals that potentially exacerbate chronic pain and reduced levels of bacteria with beneficial effects on pain. This review encourages further research to better understand the signals involved in bacteria-bacteria and bacteria-host communication to get the clues for the development of probiotics with therapeutic potential.

Sex-dimorphic neuroprotective effect of CD163 in an α-synuclein mouse model of Parkinson's disease

Alpha-synuclein (α-syn) aggregation and immune activation represent hallmark pathological events in Parkinson's disease (PD). The PD-associated immune response encompasses both brain and peripheral immune cells, although little is known about the immune proteins relevant for such a response. We propose that the upregulation of CD163 observed in blood monocytes and in the responsive microglia in PD patients is a protective mechanism in the disease. To investigate this, we used the PD model based on intrastriatal injections of murine α-syn pre-formed fibrils in CD163 knockout (KO) mice and wild-type littermates. CD163KO females revealed an impaired and differential early immune response to α-syn pathology as revealed by immunohistochemical and transcriptomic analysis. After 6 months, CD163KO females showed an exacerbated immune response and α-syn pathology, which ultimately led to dopaminergic neurodegeneration of greater magnitude. These findings support a sex-dimorphic neuroprotective role for CD163 during α-syn-induced neurodegeneration.

α-Synuclein pathology disrupts mitochondrial function in dopaminergic and cholinergic neurons at-risk in Parkinson's disease

Background

Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson's disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain.

Methods

aSYN PPFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell- type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser- scanning microscopy of genetically encoded sensors for bioenergetic and redox status.

Results

In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure.

Conclusions

Taken together, our findings suggest that disruption of mitochondrial function, and the subsequent bioenergetic deficit, is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD.

Gut liver brain axis in diseases: the implications for therapeutic interventions

Gut-liver-brain axis is a three-way highway of information interaction system among the gastrointestinal tract, liver, and nervous systems. In the past few decades, breakthrough progress has been made in the gut liver brain axis, mainly through understanding its formation mechanism and increasing treatment strategies. In this review, we discuss various complex networks including barrier permeability, gut hormones, gut microbial metabolites, vagus nerve, neurotransmitters, immunity, brain toxic metabolites, β-amyloid (Aβ) metabolism, and epigenetic regulation in the gut-liver-brain axis. Some therapies containing antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), polyphenols, low FODMAP diet and nanotechnology application regulate the gut liver brain axis. Besides, some special treatments targeting gut-liver axis include farnesoid X receptor (FXR) agonists, takeda G protein-coupled receptor 5 (TGR5) agonists, glucagon-like peptide-1 (GLP-1) receptor antagonists and fibroblast growth factor 19 (FGF19) analogs. Targeting gut-brain axis embraces cognitive behavioral therapy (CBT), antidepressants and tryptophan metabolism-related therapies. Targeting liver-brain axis contains epigenetic regulation and Aβ metabolism-related therapies. In the future, a better understanding of gut-liver-brain axis interactions will promote the development of novel preventative strategies and the discovery of precise therapeutic targets in multiple diseases.

Cytokine activity in Parkinson's disease

The contribution of the immune system to the pathophysiology of neurodegenerative Parkinson's disease (PD) is increasingly being recognised, with alterations in the innate and adaptive arms of the immune system underlying central and peripheral inflammation in PD. As chief modulators of the immune response, cytokines have been intensely studied in the field of PD both in terms of trying to understand their contribution to disease pathogenesis, and if they may comprise much needed therapeutic targets for a disease with no current modifying therapy. This review summarises current knowledge on key cytokines implicated in PD (TNFα, IL-6, IL-1β, IL-10, IL-4 and IL-1RA) that can modulate both pro-inflammatory and anti-inflammatory effects. Cytokine activity in PD is clearly a complicated process mediated by substantial cross-talk of signalling pathways and the need to balance pro- and anti-inflammatory effects. However, understanding cytokine activity may hold promise for unlocking new insight into PD and how it may be halted.

The Role of Atypical Chemokine Receptors in Neuroinflammation and Neurodegenerative Disorders

Neuroinflammation is associated with several neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation provides protection in acute situations but results in significant damage to the nervous system if chronic. Overexpression of chemokines within the brain results in the recruitment and activation of glial and peripheral immune cells which can propagate a cascading inflammatory response, resulting in neurodegeneration and the onset of neurodegenerative disorders. Recent work has identified the role of atypical chemokine receptors (ACKRs) in neurodegenerative conditions. ACKRs are seven-transmembrane domain receptors that do not follow canonical G protein signaling, but regulate inflammatory responses by modulating chemokine abundance, location, and availability. This review summarizes what is known about the four ACKRs and three putative ACKRs within the brain, highlighting their known expression and discussing the current understanding of each ACKR in the context of neurodegeneration. The ability of ACKRs to alter levels of chemokines makes them an appealing therapeutic target for neurodegenerative conditions. However, further work is necessary to understand the expression of several ACKRs within the neuroimmune system and the effectiveness of targeted drug therapies in the prevention and treatment of neurodegenerative conditions.

Central and peripheral innate and adaptive immunity in Parkinson's disease

Parkinson's disease (PD) is a multisystem disorder with characteristics of a chronic inflammatory disease. To develop effective immunomodulatory interventions to combat PD, we need to think innovatively about the implications of orchestrated central and peripheral innate and adaptive immune responses that occur as the disease begins and progresses.

Interaction of an α-synuclein epitope with HLA-DRB1∗15:01 triggers enteric features in mice reminiscent of prodromal Parkinson's disease

Enteric symptoms are hallmarks of prodromal Parkinson's disease (PD) that appear decades before the onset of motor symptoms and diagnosis. PD patients possess circulating T cells that recognize specific α-synuclein (α-syn)-derived epitopes. One epitope, α-syn32-46, binds with strong affinity to the HLA-DRB1∗15:01 allele implicated in autoimmune diseases. We report that α-syn32-46 immunization in a mouse expressing human HLA-DRB1∗15:01 triggers intestinal inflammation, leading to loss of enteric neurons, damaged enteric dopaminergic neurons, constipation, and weight loss. α-Syn32-46 immunization activates innate and adaptive immune gene signatures in the gut and induces changes in the CD4+ TH1/TH17 transcriptome that resemble tissue-resident memory (TRM) cells found in mucosal barriers during inflammation. Depletion of CD4+, but not CD8+, T cells partially rescues enteric neurodegeneration. Therefore, interaction of α-syn32-46 and HLA-DRB1∗15:0 is critical for gut inflammation and CD4+ T cell-mediated loss of enteric neurons in humanized mice, suggesting mechanisms that may underlie prodromal enteric PD.

Cytokine Profiling in Human iPSC-Derived Dopaminergic Neuronal and Microglial Cultures

Aside from the degeneration of dopaminergic neurons, inflammation is a key component in the movement disorder Parkinson's disease (PD). Microglia activation as well as elevated cytokine levels were observed in the brains of PD patients, but the specific role of microglia in the disease process is unknown. Here, we generate human cellular models by differentiating iPSCs into dopaminergic neurons and microglia. We combine these cells in co-culture to perform cytokine profiling, representing the final functional outcome of various signaling pathways. For this, we used unstimulated conditions and treatment with inflammatory stressors. Importantly, only co-cultures but not the monocultures responded to IL-1β treatment suggesting co-culture-related crosstalk. Moreover, we identified the main types of released cytokines and chemokines in this model system and found a preference for the activation of the chemotaxis pathway in response to all treatments, which informs future studies on the cell-type-specific reaction to inflammatory stimulation. Finally, we detected protein level changes in PD risk factor GPNMB upon stress in microglia, further confirming the link between PD-associated genes and inflammation in human-derived cellular models.

Neuroprotective effect of chlorogenic acid on Parkinson's disease like symptoms through boosting the autophagy in zebrafish

Parkinson's disease (PD) is characterized by both motor and non-motor symptoms, including hypokinesia, postural instability, dopaminergic (DA) neurons loss, and α-synuclein (α-syn) accumulation. A growing number of patients show negative responses towards the current therapies. Thus, preventative or disease-modifying treatment agents are worth to further research. In recent years, compounds extracted from natural sources become promising candidates to treat PD. Chlorogenic acid (CGA) is a phenolic compound appearing in coffee, honeysuckle, and eucommia that showed their potential as antioxidants and neuroprotectors. In this study, we investigated the anti-PD activity of CGA by testing its effect on 1-methyl-4-phenyl-1-1,2,3,6-tetrahydropyridine (MPTP) zebrafish model of PD. It was shown that CGA relieved MPTP-induced PD-like symptoms including DA neurons and blood vessel loss, locomotion reduction, and apoptosis events in brain. Moreover, CGA modulated the expression of PD- and autophagy-related genes (α-syn, lc3b, p62, atg5, atg7, and ulk1b), showing its ability to promote the autophagy which was interrupted in the PD pathology. The unblocked effect of CGA on autophagy was further verified in 6-hydroxydopamine (6-OHDA)-modeled SHSY5Y cells. Our findings indicated that CGA might relieve PD by boosting the autophagy in neuronal cells that makes CGA a potential candidate for anti-PD treatment.

Myeloid Cells As a Promising Target for Brain-Bone Degenerative Diseases from a Metabolic Point of View

Brain and bone degenerative diseases such as Alzheimer's disease and osteoporosis are common in the aging population and lack efficient pharmacotherapies. Myeloid cells are a diverse group of mononuclear cells that plays important roles in development, immune defense, and tissue homeostasis. Aging drastically alters the expansion and function of myeloid cells, which might be a common pathogenesis of the brain-bone degenerative diseases. From this perspective, the role of myeloid cells in brain-bone degenerative diseases is discussed, with a particular focus on metabolic alterations in myeloid cells. Furthermore, targeting myeloid cells through metabolic regulation via drugs such as metformin and melatonin is proposed as a potential therapy for the clinical treatment of brain-bone diseases.

Microglia in neurodegenerative diseases: mechanism and potential therapeutic targets

Microglia activation is observed in various neurodegenerative diseases. Recent advances in single-cell technologies have revealed that these reactive microglia were with high spatial and temporal heterogeneity. Some identified microglia in specific states correlate with pathological hallmarks and are associated with specific functions. Microglia both exert protective function by phagocytosing and clearing pathological protein aggregates and play detrimental roles due to excessive uptake of protein aggregates, which would lead to microglial phagocytic ability impairment, neuroinflammation, and eventually neurodegeneration. In addition, peripheral immune cells infiltration shapes microglia into a pro-inflammatory phenotype and accelerates disease progression. Microglia also act as a mobile vehicle to propagate protein aggregates. Extracellular vesicles released from microglia and autophagy impairment in microglia all contribute to pathological progression and neurodegeneration. Thus, enhancing microglial phagocytosis, reducing microglial-mediated neuroinflammation, inhibiting microglial exosome synthesis and secretion, and promoting microglial conversion into a protective phenotype are considered to be promising strategies for the therapy of neurodegenerative diseases. Here we comprehensively review the biology of microglia and the roles of microglia in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, multiple system atrophy, amyotrophic lateral sclerosis, frontotemporal dementia, progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies and Huntington's disease. We also summarize the possible microglia-targeted interventions and treatments against neurodegenerative diseases with preclinical and clinical evidence in cell experiments, animal studies, and clinical trials.

Systemic Inflammatory Response Index (SIRI) at Baseline Predicts Clinical Response for a Subset of Treatment-Resistant Bipolar Depressed Patients

Background: in a recent double-blind, placebo controlled RCT we demonstrated that selective inhibition of cyclo-oxygenase 2 (COX2) is an effective adjunctive strategy in treatment-resistant bipolar depression (TRBDD). To better clarify the mechanisms underlying TRBDD and treatment response, we conducted a retrospective exploratory analysis of the systemic inflammatory response index (SIRI = absolute neutrophils × absolute monocytes/absolute lymphocytes) in relation to other biomarkers and clinical outcomes after escitalopram (ESC), combined with the COX-2 inhibitor, celecoxib (CBX), versus placebo. Methods: Baseline measures of SIRI were compared between TRBDD and healthy controls (HC), and correlated with blood-based inflammatory cytokines, kynurenines, and growth factors. Post-treatment Hamilton Depression Rating Scale 17 (HAMD-17) total scores (clinical outcome) were modelled according to SIRI adjusting for demographics (including relevant interactions with SIRI), baseline depression, treatment arm, and treatment timepoint using multiple linear regression and robust linear mixed effects models. Results: Baseline SIRI did not distinguish TRBDD from HC groups. Baseline SIRI was significantly correlated with lower baseline MCP-1. The relationship between SIRI and HAMD-17 was significant at treatment week 8, in contrast to baseline. Finally, baseline SIRI predicted elevated post-treatment HAMD-17 scores, amongst patients with elevated depression scores at baseline. Significance: High pre-treatment SIRI may predict poorer depressive outcomes amongst TRBDD patients with baseline elevated depression.

Myeloid-specific blockade of notch signaling alleviates dopaminergic neurodegeneration in Parkinson's disease by dominantly regulating resident microglia activation through NF-κB signaling

Yolk sac-derived microglia and peripheral monocyte-derived macrophages play a key role during Parkinson's disease (PD) progression. However, the regulatory mechanism of microglia/macrophage activation and function in PD pathogenesis remains unclear. Recombination signal-binding protein Jκ (RBP-J)-mediated Notch signaling regulates macrophage development and activation. In this study, with an 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) hydrochloride-induced acute murine PD model, we found that Notch signaling was activated in amoeboid microglia accompanied by a decrease in tyrosine hydroxylase (TH)-positive neurons. Furthermore, using myeloid-specific RBP-J knockout (RBP-JcKO) mice combined with a PD model, our results showed that myeloid-specific disruption of RBP-J alleviated dopaminergic neurodegeneration and improved locomotor activity. Fluorescence-activated cell sorting (FACS) analysis showed that the number of infiltrated inflammatory macrophages and activated major histocompatibility complex (MHC) II+ microglia decreased in RBP-JcKO mice compared with control mice. Moreover, to block monocyte recruitment by using chemokine (C-C motif) receptor 2 (CCR2) knockout mice, the effect of RBP-J deficiency on dopaminergic neurodegeneration was not affected, indicating that Notch signaling might regulate neuroinflammation independent of CCR2+ monocyte infiltration. Notably, when microglia were depleted with the PLX5622 formulated diet, we found that myeloid-specific RBP-J knockout resulted in more TH+ neurons and fewer activated microglia. Ex vitro experiments demonstrated that RBP-J deficiency in microglia might reduce inflammatory factor secretion, TH+ neuron apoptosis, and p65 nuclear translocation. Collectively, our study first revealed that RBP-J-mediated Notch signaling might participate in PD progression by mainly regulating microglia activation through nuclear factor kappa-B (NF-κB) signaling.

The Molecular Mechanisms of the Relationship between Insulin Resistance and Parkinson's Disease Pathogenesis

Parkinson's disease (PD) is a degenerative condition resulting from the loss of dopaminergic neurons. This neuronal loss leads to motor and non-motor neurological symptoms. Most PD cases are idiopathic, and no cure is available. Recently, it has been proposed that insulin resistance (IR) could be a central factor in PD development. IR has been associated with PD neuropathological features like α-synuclein aggregation, dopaminergic neuronal loss, neuroinflammation, mitochondrial dysfunction, and autophagy. These features are related to impaired neurological metabolism, neuronal death, and the aggravation of PD symptoms. Moreover, pharmacological options that involve insulin signaling improvement and dopaminergic and non-dopaminergic strategies have been under development. These drugs could prevent the metabolic pathways involved in neuronal damage. All these approaches could improve PD outcomes. Also, new biomarker identification may allow for an earlier PD diagnosis in high-risk individuals. This review describes the main pathways implicated in PD development involving IR. Also, it presents several therapeutic options that are directed at insulin signaling improvement and could be used in PD treatment. The understanding of IR molecular mechanisms involved in neurodegenerative development could enhance PD therapeutic options and diagnosis.